Sometimes people create a new blank e-mail to respond to an old email conversation, which makes my job more difficult because I have to find the last conversation to remember what they are talking about.

What is the best way to fix this?

I want Gmail to show emails in the inbox by email-address. If that makes any sense, i.e., in the inbox I want to see emails by sender, and when I click on a line in the inbox, it will show me all that the person ever sent me, in only one page.